How to update some columns of multi rows in PostgreSQL - postgresql

Question

I have a table called Configuration. The 1st column of the table is deviceId, the 2nd column is parameter, 3rd column is value.
In the table, there are many devices, each device has only one device ID(column 1); each device has many config parameters(column 2), ex. VER, DATE, COMPANY etc, all devices have the same config parameters; the parameter's value(column 3) for different devices may be the same or not.
I want to update two config parameters say VER and DATE with new parameter's values(column 3) for the device which has ID equal to "id12345".
How can I achieve this in one PostgreSQL query?

Answer 1

This is what you could do, although I don't think it's a terrific idea.
UPDATE configuration
SET value =
CASE parameter
WHEN 'VER' THEN new_ver_value
WHEN 'DATE' THEN new_date_value
END
WHERE deviceid = 'id12345';
Parameter tables like this are generally considered a bad idea, as the complexity of this query helps illustrate. Also, since you say that all the devices have the same parameters, doing this instead of having a unique column for each parameter doesn't seem to achieve anything useful.
Also if possible use just a number for the deviceid instead of a string.
As requested, to update an additional field, like a time field set to the current_time, you could do the following.
UPDATE configuration
SET value =
CASE parameter
WHEN 'VER' THEN new_ver_value
WHEN 'DATE' THEN new_date_value
END,
time = current_time
WHERE deviceid = 'id12345'
AND parameter IN ('VER', 'DATE');
For the first query, here is a test to show the result.
CREATE TABLE configuration
(deviceid CHARACTER VARYING (20),
parameter CHARACTER VARYING (10),
VALUE integer);
INSERT INTO configuration
(VALUES ('id12345', 'VER', 1),
('id12345', 'DATE', 20190101),
('id12345', 'COMPANY', 55),
('id33333', 'VER', 2),
('id33333', 'DATE', 20180101),
('id33333', 'COMPANY', 6));
SELECT * FROM configuration;
id12345 VER 1
id1234 DATE 20190101
id12345 COMPANY 55
id33333 VER 2
id33333 DATE 20180101
id33333 COMPANY 6
UPDATE configuration
SET value =
CASE parameter
WHEN 'VER' THEN 11
WHEN 'DATE' THEN 2020010
END
WHERE deviceid = 'id12345'
AND parameter IN ('VER', 'DATE');
SELECT * FROM configuration;
id12345 COMPANY 55
id33333 VER 2
id33333 DATE 20180101
id33333 COMPANY 6
id12345 VER 11
id12345 DATE 2020010